STUDIES  OF  INSECTS  AFFECTING  THE  PRODUCTION 
OF  RED  CLOVER  SEED 

BY 

FAUSTINO  QUESALES  OTANES 
B.  Agr.  University  of  the  Philippines,  1918 
A.  B.  University  of  Illinois,  1921 


THESIS 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of 

MASTER  OF  SCIENCE 
IN  ENTOMOLOGY 

IN 

THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 
1922 


mj= 


UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 


January  19,  1 922_ 


I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 

SUPERVISION  BY Faustlno  (^uesaXea  Xitanea 

ENTITLED  ^ Studies  „pf  Insec ta -Af f^ctln^  -the  EroductLon 

of  Red  Clover  Seed. 

BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF Master. of  Science.  


Recommendation  concurred  in* 


Committee 


on 


Final  Examination* 


^Required  for  doctor’s  degree  but  not  for  master’s 


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1 

TABLE  OP  CONTENTS 

PAGE 

I.  INTRODUCTION, - - 2 

II.  METHODS, - 4 

III.  DATES  OP  CLIPPING  OP  THE  PLOTS,--  — - . — -5 

IV.  RELATION  OP  CLIPPING  TO  NUIIBERS  OP  INSECTS— — 5 

t.  DISCUSSION  OP  THE  ABUNDANCE  OP  PESTS  STUDIED 7 

1.  The  Clover  Seed-Midge--' .-.7 

2.  The  Clover  Seed-Chalcid-' 10 

3.  The  Clover  Seed-Caterpillar- 12 

VI.  RELATION  OP  CLIPPING  AND  ABUNDANCE  OP  PESTS  TO  THE 

YIELD  OP  SEED 

VII.  THE  LESSER  CLOVER  LEAP-WEEVIL 15 

1.  General  Importance--^ I5 

2.  Origin  and  Distribution--^ 15 

3.  Present  Distribution  of  the  Species  in  the 

United  States--- 16 

4.  Pood  Plants- — - — 1? 

5.  The  Species  in  Illinois 17 

6.  Nature  and  Extent  of  Injury 17 

7.  Life  History  and  Habits-- 20 

8.  Abundance 22 

9.  Natural  Enemies — 25 

VIII.  POLLINATION  OP  RED  CLOVER- 29 

1.  Insects  Observed  Working  on  Clover  Heads 29 

2.  Comparison  of  the  Activity  of  Bees 34 

3«  Experiments  on  Pollination  of  Red  Clover 37 

Experiment  with  Tetralonla  dilecta  Cress. — 37 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/studiesofinsectsOOotan 


1 a 

TABLE  OF  CONTEI'JTS  ( CONT . ) 

PAGE 

Experiments  on  Pollination  of  Red  Clover 

Experiment  with  Meliesodes  bimacula ta  Le  P.--38 

Experiment  with  Exoprosopa  prorsa -40 

Experiment  with  Mep;achile  brevis  Say — • — 40 

Controls -41 


2 


STUDIES  OP  INSECTS  AFFECTING  THE  PRODUCTION 
OP  RED  CLOVER  SEED 

I.  INTRODUCTION 

With  soil  and  weather  conditions  all  favorable  to  the  growth 
and  flowering  of  red  clover,  a low  yield  of  seed  can  be  attributed 

to 

chiefly^ two  factors,  namely,  the  absence  or  scarcity  of  insect 
pollinators  and  the  abundance  of  insects  thatiaffect  the  seeds  di- 
rectly. The  most  important  insects  that  infest  the  heads  of  clover 
are  the  clover  seed-midge  (Pasyneura  lep;uminicola  Lint.}^  the  clover 
seed-chalcid  (Bruchophagug  _funebris  Hpw.  ) . and  the  clover  seed-cater- 
pillar (Enannonla  inters tine tana  Clem.).  It  is  the  object  of  this 
paper  to  present  the  observations  that  were  made  on  these  pests 
during  the  spring  and  summer  of  1921  in  the  hope  that  they  will  be 
of  some  value  to  workers  engaged  in  the  control,  or  in  the  study  of 
the  control,  of  these  clover  pests.  The  points  especially  dealt 
with  in  this  paper  are  the  periodic  abundance  of  these  insects  and 
the  relation  of  such  abundance  to  the  production  of  red  clover  seed, 
and  the  control  of  Insects  by  means  of  pasturing,  clipping,  or  early 
cutting  of  the  June  hay  crop. 

with  a limited  time  at  his  disposal,  there  has  been  no  attempt 
on  the  part  of  the  writer  to  cover  every  phase  of  the  subject.  For 
example,  he  has  not  gone  Into  a detailed  study  of  the  life  histories 
and  descriptions  of  the  pests  dealt  with,  as  the  results  of  accurate 
Investigations  that  have  been  published  on  these  subjects  by  previous 
workers,  both  In  and  outside  the  state  of  Illinois,  have  made  such  a 
study  unnecessary.  Anyone  interested  In  the  most  Important  insect 


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pests  of  red  clover,  particularly  the  three  mentioned  here,  will 
find  a detailed  and  accurate  account  of  them,  especially  as  regards 
life  history,  descriptions  and  control,  in  Bulletin  134,  by  Dr.  J.  W 
Folsom,  published  in  1909  by  the  University  of  Illinois  Agricultural 
Experiment  Station.  (See  also  1909  Report  of  the  State  Entomologist 
of  Illinois  for  the  same  article  by  Dr.  PolsonU 

In  the  present  paper  an  account  of  observations  made  by  the  writ- 
er on  the  lesser  clover  leaf-weevil  (Phytonomus  nigrlrostris  Fab. } 
is  Included,  however,  since  so  far  as  the  writer  knows,  no  data  have 
been  published  in  regard  to  the  occurrence  and  work  of  this  Insect 
in  Illinois.  There  are  also  included  in  this  paper  some  observatione 
on  pollinating  insects,  with  special  reference  to  results  of  experl-, 
ments  performed  showing  the  possibility  of  red  clover  being  polli-  * 
nated  by  bees  other  than  bumblebees  and  honey  bees. 

This  investigation  was  done  under  the  direction  of  Dr.  J.  W.  Fol- 
som and  to  him  I desire  to  express  my  thanks  for  his  constant  advice 
and  suggestions  and  for  certain  data  on  pollination.  I desire  also 
to  express  my  thanks  to  Mr.  W.  P.  Flint  for  putting  at  my  disposal 
the  records  of  observations  that  were  made  during  the  last  two  years, 
1919  and  1920.  My  thanks  are  also  due  to  Dr.  C.  P.  Alexander  for  the 
Identification  of  certain  specimens. 


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II.  METHODS 

These  observations,  which  were  begun  In  the  latter  part  of  April 
1921,  were  made  on  a clover -field  on  the  South  Farm  of  the  Universi- 
ty of  Illinois.  This  field  is  one  of  a series  of  plots  which  is 
being  used  by  the  experiment  Station  in  crop  rotation  investigations 
and  bears  the  serial  number  700.  It  is  subdivided  into  eighteen 
one- fifth  acre  plots,  each  of  2 by  16  rods,  numbered  consecutively 
from  741  to  758  inclusive,  from  north  to  south.  Its  total  area  is 
three  and  three- fifths  acres.  It  was  sown  to  clover  in  1920  and  was 
therefore  in  the  second  year  of  its  growth  at  the  time  my  studies 
were  made. 

In  studying  the  abundance  of  the  seed-infesting  insects,  a 
strip  about  four  feet  wide  throughout  the  west  edge  of  this  field 
was  swept  with  an  insect  net,  usually  every  other  day,  on  Tuesdays, 
Thursdays,  and  Saturdays,  in  the  forenoon  from  10  to  12  o'clock  as 
a rule.  The  Insects  collected,  which  were  desired  for  the  purposes 
of  this  Investigation,  were  picked  from  the  net  by  means  of  a pair 
of  forceps  and  put,  in  most  cases,  together  in  vials  containing 
about  70  per  cent,  of  denatured  alcohol.  They  were  then  sorted  out 
in  the  laboratory  and  the  number  of  Individuals  of  each  species  was 
counted  and  recorded. 

In  sweeping  the  field  with  the  net,  the  pacing  was  made  as  uni- 
form as  possible,  as  the  length  of  the  steps  has  a direct  relation 
to  the  number  of  strokes  with  the  net,  and  a wide  variation  in  the 
number  of  strokes  in  the  sweepings  would  materially  affect  the  re- 
sults. 

The  data  obtained  on  the  variation  in  abundance  in  this  locali- 


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ty  of  the  insects  studied  are  here  presented  in  the  form  of  graphs. 
In  discussing  the  results,  it  is  desirable  to  deal  with  each  species 
separately. 

III.  DATES  OP  CLIPPING  OP  THE  PLOTS 

On  May  10  the  plants  were  forming  buds.  A week  later,  May  17, 
the  heads  were  beginning  t6  show  the  pink,  and  some  were  in  full 
bloom  on  May  19. 

May  19,  plot  741  was  clipped  and  was  again  clipped  on  June  13. 

Plot  742  was  clipped  on  May  31. 

June  16,  plots  743  and  745  to  758  Inclusive,  were  clipped,  in- 
cluding the  strip  along  the  west  edge  of  the  field  that  was  being 
swept. 

Plot  744  was  left  undipped. 

Herafter  only  plots  741  to  749  inclusive,  will  be  considered, 
as  these  were  the  only  plots  from  which  seed  were  extracted,  the 
plants  on  plots  750  to  758,  inclusive,  being  cut  for  hay. 

Thus  of  all  the  plots,  only  one.  No.  741,  was  double- clipped; 
one  plot,  744,  being  left  undipped,  and  all  the  others  single- 
clipped. 

IV.  RELATION  OP  CLIPPING  TO  NUMBERS  OP  INSECTS 

The  clipping  on  June  16  of  the  strip  that  was  being  swept  ne- 
cessarily affected  the  collection  of  insects,  especially  the  clover 
seed-chalcid.  It  did  not,  however,  affect  the  seed-midge,  as  the 
flies  had  already  disappeared  two  weeks  before  June  16.  It  affected 
the  lesser  clover  leaf“weevil  to  some  extent.  More  will  be  said  on 
this  subject  beyond. 


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Because  of  the  clippings,  the  sweeping  of  the  strip  was  dis- 
continued, as  the  number  of  individuals  of  each  species  collected 
therefrom  would  be  too  low,  and  the  figures  obtained  would  not  give 
a good  indication  of  the  abundance  of  each  species.  Instead  of 
sweeping  this  area,  a strip  about  24  feet  long  and  of  the  same  width 
as  the  original  strip,  four  feet,  on  the  north  edge  of  the  undipped 
plot,  plot  744,  was  swept  and  the  figures  obtained  were  used  in  com- 
puting the  number  of  individuals  for  the  original  strip.  An  ob- 
jection to  this  method  is  that  the  figures  would  be  too  high,  es- 
pecially in  the  case  of  the  chalcids,  as  their  tendency  would  be  to 
concentrate  upon  the  plots  which  were  not  clipped  on  June  16,  where 
they  could  find  heads  in  which  to  oviposit. 

On  July  7,  the  clover  heads  in  plot  742  were  in  just  the  right 
condition  for  oviposition  by  the  chalcids.  The  insects  were  then 
observed  in  numbers  as  in  plot  744.  Beginning  July  7,  a strip  in 
plot  742  of  the  same  size  as  that  in  744  was  swept,  the  sweeping  in 
744  being  continued  until  July  21,  The  clover  on  744  was  cut  for 
seed  on  July  30. 

The  averages  of  the  collections  from  the  two  strips  from  July 
7 to  21  were  taken  and  the  figures  were  used  in  computing  the  number 
of  individuals  for  the  original  strip.  The  computations  of  the  num- 
ber of  individuals  for  the  original  strip  from  July  21  to  August  5 
were  based  on  collections  from  the  strip  in  742  alone. 

Beginning  August  3,  a strip  about  four  feet  wide  along  the  west 
edges  of  plots  745  to  749  Inclusive  was  swept.  The  sweepings  in  plot 
742  were  continued,  however,  until  August  18. 

August  20,  the  clover  on  plots  741,  742,  7 4 3^ and  745  to  749  in- 
clusive was  cut  for  seed.  Beginning  August  20  and  thereafter  the 


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7 


entire  original  strip  was  swept. 

V.  DISCUSSION  OP  THE  ABUNDANCE  OP  PESTS 

STUDIED 

1.  THE  CLOVER  SEED-MIDGE 
(Dasyneura  leguminicola  Lint. ) 

Graph  No.  I shows  the  results  obtained  for  the  clover  seed-midge, 
In  central  Illinois  tv/o  full  broods  of  the  seednmidge  are  known. 
There  is  also  a feeble  third  generation  of  flies  which  properly  be- 
longs to  the  May,  or  first^ brood  of  the  next  year.  The  midges  of 
the  first  generation  during  the  past  season  were  first  collected  on 
May  10,  two  individuals  having  been  collected  on  that  day  with  the 
net.  On  May  12,  ten  were  collected;  then  there  was  a drop  in  the 
collections  to  three  and  two  on  May  14  and  1?  respectively.  The 
number  collected  jumped  suddenly  to  forty- five  on  May  19  and  then, 
on  May  21,  to  one  hundred  and  twenty- six,  the  maximum  number  col- 
lected. The  drop  in  the  number  collected  three  days  later.  May  24, 
was  as  sudden  as  the  rise,  fifty-tv;o  having  been  collected  on  that 
day.  On  May  27  and  28,  the  midges  were  scarce;  only  one  individual 
being  collected  on  each  of  these  days.  The  flies  disappeared  three 
days  later,  as  the  record  shows. 

The  flies  of  the  second  generation  began  to  appear  about  August 
18,  but  were  not  abundant,  five  being  the  maximum  number  collected, 
and  this  occurred  on  August  25.  This  scarcity  of  flies  was  probably 
due  to  the  clippings  of  the  clover. 


Thus,  according  to  these  observations,  the  midges  were  on  the 
wing  during  the  past  season  on  May  ^0,  reaching  their  maximum  a- 
bundance  on  May  21,  and  disappearing  after  a week.  The  flies  of  the 


r»i' f» -.-I  ♦ '•  4';  ■ f*®**’*'^  - :•;  '•'!/“  «lr'-  ’. '•.  ^ 

i ‘ • ■*..  .'■"•  , st,*  , ; ••  e.vc 

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<««wk^=  VI*. ».-.«<  /i  w. . ..A.  1'  .v>4  4 vi»4i4  , t /■•V.;':  I^)>'  ' ltJ 


R'^’'^''-  -"  ' * i'  • ' ' i ’■'  .■’  ‘ '■  'V'  ■ ’ ‘''  *' 


8 


first  generation  were  thus  on  the  wing  for  a period  of  approxi- 
mately three  weeks.  The  dates  of  appearance  and  of  maximum  a- 
bundance  of  the  midges  for  the  past  season  are  rather  early,  con- 
sidering  previous  observations  for  this  locality.  Dr.  J.  W.  Folsom, 
in  1907,  did  not  find  the  midges  until  May  15;  they  were  common 
May  23,  but  did  not  reach  their  maximum  abundance  until  May  30.  Dr. 
Folsom  attributed  this  to  the  lateness  of  the  season  that  year,  due 
to  prolonged  cold  weather  in  April.  In  1903  to  1906  Inclusive,  ac- 
cording to  Dr.  Folsom,  the  dates  of  maximum  abundance  were  May  24 
and  25,  the  time  when  the  young  greeiiclover  heads  were  most  abun- 
dant. Unpublished  observations  by  Mr.  Spooner,  under  the  direction 
of  Mr.  W.  P.  Flint,  entomologist  of  the  Natural  History  Survey,  for 
the  last  two  years,  1919  and  1920,  show  that  in  1919,  the  flies 
were  on  the  wing  May  15,  reaching  their  maximum  abundance  May  31 
and  disappearing  June  3.  In  1920,  the  date  of  appearance  was  late, 
the  midges  having  been  collected  first  on  May  24.  They  reached 
their  maximum  abundance  two  days  later.  May  26,  and  disappeared 
I after  two  weeks.  Judging  from  these  observations,  the  adults  of 
the  first  generation  may  be  expected  in  the  second  week  of  May  or 
earlier. 

The  larvae  of  the  first  generation  of  the  clover  seed-midge  were 
at  work  in  the  heads  during  the  last  days  of  May  and  during  June. 

On  June  4,  the  midges  were  abundant  in  the  heads,  26  larvae  having 
emerged  from  ten  clover  heads  in  full  bloom.  It  is  known  that  the 
larvae  of  the  first  generation  may  be  found  working  in  clover  heads 
as  late  as  the  first  week  of  July  and  even  later. 

A fairly  accurate  estimate  of  the  amount  of  Infestation  by  the 
midge  larvae  may  be  obtained  by  putting  the  infested  clover  heads 


f ■; 


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9 


in  a corked  bottle  and  then  counting  the  number  of  larvae  that 
emerge  from  the  clover  heads.  Mere  examination  of  the  heads  by 
tearing  off  the  florets  will  not  show  all  of  the  larvae  or  may  show 
none  at  all.  In  the  case  referred  to  previously,  in  which  26  lar- 
vae were  obtained  from  ten  heads,, mere  examination  of  the  heads  by 
tearing  off  the  florets  disclosed  only  three  larvae,  whereas  when 
these  same  heads  were  put  in  a tightly  corked  bottle  a total  of 
26  larvae  was  obtained. 

The  larvae  of  the  flies  of  the  second  generation,  according 
to  Dr.  Folsom,  are  most  abundant  during  the  last  two  weeks  of 
August  and  the  first  two  weeks  of  September,  and  it  is  during  this 
time  that  they  do  most  damage.  Most  of  these  larvae  pass  the  winter 
either  as  larvae  or  pupae.  A few  of  the  larvae,  however,  are  said 
to  attain  their  full  growth  early  enough  to  produce  flies  in  early 
September  or  even  later. 

As  to  when  the  larvae  of  the  second  generation  leave  the  heads 
to  pupate  in  the  soil,  I do  not  find  any  definite  statement  for  cen- 
tral Illinois.  They  may  remain  in  the  heads  until  the  middle  of 
October  or  even  later,  depending  upon  the  weather.  In  1919,  the 
writer  observed  the  larvae  still  common  in  blover  heads  on  October 
3,  and  in  1921  they  were  still  found  in  considerable  numbers  on 
October  6. 

In  the  laboratory,  with  artificial  heat,  the  flies  may  emerge 
any  time  during  the  fall  and  winter.  Thus, ^In  1919,  larvae  col- 
lected on  October  3 gave  adults  on  October  2?  and  November  3;  and 
in  1921,  larvae  collected  October  6 gave  adults  in  December  and  in 
January  3,  1922. 


I 


r. 


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f’  Kiv  ■ "'.'  ^ 


10 


2.  THE  CLOVER  SEED-CHALCID 
(Bruchophap;us  funebris  How. ) 

Adults  of  this  species  were  first  collected  on  May  19,  six  in- 
dividuals having  been  caught  with  the  net  on  that  day.  There  was 
a gradual  Increase  for  two  succesive  sweepings  on  May  21  and  24,  the 
number  of  Individuals  collected  being  14  and  16  respectively.  Then 
a drop  in  the  collections  followed,  the  curve  maintaining  an  almost 
constant  level  for  three  successive  sweepings,  and  then  dropping 
suddenly,  and  eventually  to  zero  on  June  13* 

As  has  been  stated  elsewhere,  the  strip  which  was  being  swept 
was  clipped  on  June  16.  This  affected  the  collections,  as  the  chal- 
cids  naturally  concentrated  on  plots  741,  742  and  744,  especially 
on  744,  where  there  were  heads  )sui table  for  oviposltion.  The  con- 
centration of  the  chalcids  on  plot  744  may  be  taken  as  a reason  for 
such  a sudden  rise  in  the  collection,  as  shown  in  curve  A,  graph  II, 
from  zero  on  June  13  to  over  200  on  June  22.  The  figures  obtained 
from  the  sweepings  in  plots  744,  742  and  the  strip  comprising  the 
west  edges  of  plots  745  to  749, inclusive, were  used  in  computing  the 
number  of  individuals  that  would  have  been  collected  from  the  ori- 
ginal strip.  It  is  from  such  computations  that  curve  A was  plotted. 

The  portion  of  curve  A beginning  June  16  and  continuing  up  to 
August  18  should  be  taken  as  theoretical,  being  derived  from  the 
collections  from  the  strips  in  plots  742,  744,  and  745  to  749,  in- 
clusive. 

Curve  B was  plotted  from  actual  collections  from  plots  742  and 
and  744,  iihile  curve  C from  the  actual  collections  from  the  strip 
comprising  the  west  edges  of  plots  745  to  749^ Inclusive. 


J^v'  ffl-' 


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11 


It  should  be  added  that  the  remaining  part  of  curve  A,  begin- 
ning August  20,  represents  actual  collections  from  the  whole  ori- 
ginal strip. 

As  the  preceding  observations  show,  the  chalcids  v/ere  on  the 
wing  May  19.  According  to  Dr.  Folsom  (1909),  the  chalcids  as  a rule 
do  not  begin  to  emerge  until  May  15.  Some  observations  in  previous 
years,  however,  showed  the  date  of  emergence  to  be  later  than  my 
record.  Thus,  in  1907,  Dr.  Folsom  found  no  adults  until  May  23^ 
and  in  1920,  Mr.  Spooner  did  not  collect  the  adults  until  May  26, 

On  the  contrary,  in  1919,  Mr.  Spooner  collected  the  adults  more 
than  two  v/eeks  earlier,  B5ay  10,  which  is  rather  early. 

As  the  curves  show,  the  chalcids  were  most  abundant  after  the 
middle  of  June,  the  maximum  number  collected  occurring  on  June  23, 
after  which  there  was  a sudden  decrease  in  the  number.  The  insects 
were  fairly  common  throughout  July  up  to  the  middle  of  August,  after 
which  the  adults  became  scarce.  It  is  known  that  the  chalcids  can 
be  found  from  May  15  to  October  15,  or  later,  especially  on  volunteei 
clover,  where  they  can  find  heads  at  any  time  in  just  the  right  con- 
dition for  ovlpcbition.  During  the  past  season  no  individuals  were 
found  after  October  15,  except  one,  and  this  was  collected  on  October! 


VC:  •;  ■ 


V<^11  .'10*1^..?- 


12 


3.  THE  CLOVER  SEED- CATERPILLAR 
(Enarmonia  interstinctana  Clem.) 


The  moths  of  this  species  were  not  present  in  such  numbers  as 
to  constitute  an  important  pest  in  1921.  Graph  III  shov/s  that  the 
largest  number  of  moths  collected  in  May  was  three.  On  June  22  and 
23,  the  number  collected  on  each  day  was  eight.  These  numbers  for 
June,  however,  were  not  actual  but  computed,  being  based  on  the 
numbers  collected  from  the  fifty  sweeps  made  in  plot  744.  After 
June  23,  no  more  moths  were  collected  except  on  August  12  and  16, 
three  moths  having  been  collected  on  each  of  these  days.  These  fi- 
gures for  August,  like  those  for  June,  were  computed,  being  based 
on  the  collections  from  the  strip  comprising  the  west  edges  of  plots 
745  to  749  inclusive. 

In  1920,  the  moths  were  present  in  large  numbers.  They  were 
most  abundant  during  the  last  two  weeks  of  May  and  the  first  week 
of  June,  the  maximum  number  collected  being  more  than  five  hundred. 
They  were  present  in  much  fewer  mmibers  in  July,  and  fewer  still  in 
August  of  that  year. 

On  June  30,  1921,  a hymenopterous  parasite  emrged  from  a larva 
collected  on  June  22,  1921.  This  parasite  was  identified  by  Mr.  H. 
L.  Vierlck  as  belonging  to  the  genus  Mlcrobracon. 


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13 

VI.  RELATION  OF  CLIPPING  AND  ABUNDANCE  OF  PESTS  TO  THE 

YIELD  OF_  SEED 

Plot  741  was  clipped  on  May  18,  at  a time  when  the  plants  were 
forming  buds,  when  the  clover  seed-midge  adults  were  on  the  wing, 
and  when  the  chalcids  and  lesser  clover  leaf- weevil  adults  and  lar- 
vae were  not  yet  abundant.  It  was  again  clipped  on  June  13,  at  a 
time  when  the  clover  seed  midge  larvae  were  at  work  in  the  clover 
heads  and  when  the  clover  leaf- larvae  and  adults  were  abundant.  At 
this  time  the  chalcids  were  not  as  yet  abundant.  Plot  741  was  thus 
double- clipped. 

Plot  742  was  clipped  on  May  31,  at  a time  when  the  clover  seed- 
midges  had  already  disappeared  but  when  the  larvae  of  this  species 
and  of  the  lesser  clover  leaf-weevil  were  at  work  in  the  clover  heads 
At  this  time  also,  the  chalcids  were  not  yet  abundant. 

Plots  743  and  745  to  749  inclusive  were  clipped  on  June  16. 

This  time  the  clover  seed“midge  larvae  were  at  work  in  the  clover 
heads . 

Plot  744,  as  has  been  stated  previously,  was  left  undipped. 

The  following  table  shows  the  yield  in  seed  of  these  different 
plots  in  bushels  per  acre. 


Plot  No.  Yield  in  bushels  per  acre. 

741  0.46 

742  0.64 

743- -0.80 

744  0.51 

745  - - 0.72 

746  1.00 

747  - 1.04 

748#' 0.92 

749- 0.95  ^ 


Examination  of  the  preceding  table  shows  that  the  acre  yields 


^ r 

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14 


by  plots  are  extremely  low,  far  below  the  average  in  Illinois. 

One  reason  for  these  extremely  low  yields  is  no  doubt  the  scar- 
city of  bumblebees  during  the  past  season.  A second  reason  is  pro- 
bably the  weediness  of  the  field  as  a whole,  particularly  plots  741, 
742  and  744,  and  a third  reason  is  the  somewhat  thin  stand  of  clover 
that  was  present. 

Comparison  of  the  preceding  yields  shows  several  things.  The 
double- clipped  plot,  741,  and  the  iinclipped  plot,  744,  gave  the  lo- 
west yields,  being  0.46  and  0.5I  bushels,  respectively.  $he  plots 
which  were  single-clipped,  742,  743,  and  745  to  749  inclusive,  gave 
each  a higher  yield  per  acre,  the  yield  ranging  from  0.64  to  1.04 
bushel  per  acre,  the  average  being  0.88  bushel. 

The  reason  for  the  lower  yield  in  the  undipped  plot,  744,  is 
probably  the  fact  that  the  seed-infesting  insects,  the  chalcids  es- 
pecially, concentrated  their  attacks  on  it  after  most  of  the  other 
plots  were  clipped. 


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15 


VII.  THE  LESSER  CLOVER  LEAF- WEEVIL 
(Phy tonomus  ni^rlrostrls  Fab. ) 

1 , General  Importance 

It  seems  desirable,  in  view  of  the  importance  of  the  insect,  to 
give  a brief  historical  account  of  its  origin  and  also  some  data  as 
regards  its  distribution  in  North  America,  particularly  in  the 
United  States,  so  far  as  could  be  gathered  from  the  literature. 

2.  Origin  and  Distribution 

The  lesser  clover  leaf-weevil  invaded  North  America  from  Europe, 
where  it  is  of  general  occurrence.  The  date  of  its  introduction 
into  America  is  not  definitely  known.  F.  M.  Webster,  who  published 
a detailed  historical  account  of  the  insect  in  1909,  makes  the  as- 
sumption tliat  it  first  gained  a foothold  in  Nev/  Brunswick  and  else-  1 
where  in  extreme  eastern  Canada,  his  basis  for  this  assumption  being 
that  it  first  became  destructive  in  those  sections  of  North  America. 
From  these  regions  the  pest  spread  to  other  parts  of  the  continent 
by  natural  agencies.  Webster  also  states  that  Hubbard  and  Schwarz 
collected  the  insect  in  Massachusetts  during  the  winter  of  1873-74, 
and  that  Blanchard,  one  of  the  oldest  and  most  careful  collectors  of 
New  England  Coleoptera,  is  of  the  opinion  that  it  may  have  occurred 
in  Massachusetts  as  early  as  1865.  Provancher,  in  1877,  described 
it  from  Quebec  under  the  name  of  Erirhinus  viridis.  How  long  the 
species  had  been  known  to  Provancher  prior  to  his  description  of  the 
insect  is  not  known.  Since  1873-74,  the  Insect  has  gradually  ex- 
tended its  territory.  Titus  (1911)  showed  that  the  range  of  the 
species  in  that  year  comprised  southeastern  Canada  (New  Brunswick, 


■ . N '1/ 


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16 

Ontario  and  Quebec,  Including  Prince  Edward  Is.),  the  New  England 
States,  and  extended  westward  into  Indiana  and  as  far  south  as  the 
southeastern  coast  of  Virginia.  Webster  (1909)  discussed  the  possi- 
bility  of  the  insect  having  spread  southward  through  the  agency  of 
the  Gulf  Stream,  floating  on  debris  carried  from  the  beach.  Titus, 
however,  thought  this  to  be  improbable,  stating  that  many  persons 
have  tried  the  effect  of  salt  water  on  insects  and  found  that  it  is 
rare  for  the  latter  to  surviv*  longer  than  a few  hours.  That  the 
insect  reached  the  southern  coast  by  gradual  flight,  passing  a 
little  farther  southward  year  by  year,  or  that  it  was  carried  by 
trains,  seemed  to  Titus  to  be  more  probable.  In  support  of  the 
first  possibility,  he  mentioned  Houghton's  report  on  the  spring 
flight  of  the  species  in  Delaware. 

3.  Present  Distribution  of  the  Species  in 
in  the  United  States 

The  latest  paper  giving  a detailed  accoimt  of  the  distribution 
of  the  species  was  that  by  Titus  in  1911.  According  to  him,  the 
distribution  of  the  insect  in  the  United  States,  as  then  recordE?d, 
embraced  the  following  states:  Maine,  New  Hampshire,  Vermont,  Massa- 
chusetts, Rhode  Island,  Delaware,  Connecticut,  New  York,  New  Jersey, 
Pennsylvania,  Maryland,  District  of  Columbia,  Virginia,  Michigan, 
Indiana,  and  Minnesota.  Since  1911,  so  far  as  I have  ascertained, 
there  has  not  been  any  published  record  of  the  insect  in  other  states 
except  one  by  Cooley,  who  recorded  it  from  Montana  in  1916.  It  is 
of  Interest  to  trace  the  migration  of  the  Insect  since  1911.  If  it 
has  been  present  in  Montana  since  1916,  it  is  probable  that  the 
beetle  has  been  present  also  in  other  states  east  of  Montana. 


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17 


44.  Food  Plants 

In  Europe,  Algeria,  Egypt,  and  in  Asia  Minor,  it  has  been  re*- 
corded  as  feeding  on  different  species  of  Ononis,  especially  Ononis 
spinosa.  Its  other  food  plants  in  Europe  are  Buphthalmum  salici* 
folium  and  Trifolium  pratense.  Trifolium  agrarium  has  also  been 
given  as  a probable  food  plant  of  the  insect  on  that  continent. 

In  Worth  America,  it  is  known  to  feed  on  red  clover  (Trl folium 
pratense) . mammoth  clover  (Trifolium  medium ) . alfalfa  (MedicaRO 
satlva) . crimson  clover  (Ti^l folium  incarnation ) . white  clover  (Tri- 
folium  repens) . and  alsike  clover  (Trifolium  hybridum). 

5.  The  Species  in  Illinois 

Mr.  W.  ?.  Flint,  entomologist  of  the  Illinois  Natural  History 
Survey,  observed  large  numbers  of  the  beetles  in  Urbana,  Illinois, 
in  the  fall  of  1919.  The  pest  may  have  been  present  in  Illinois 
some  years  before  this,  having  escaped  observation;  for  Titus,  in 
1911,  recorded  the  insect  as  occurring  as  far  west  as  the  western 
boundary  of  Indiana. 

Heretofore  there  has  not  been  any  published  record  and  account 
of  the  Insect  from  Illinois  since  Mr.  Flint  found  it  in  1919.  Du- 
ring 1920,  a study  of  its  abundance  was  made  by  Mr.  Spooner,  under 
Mr.  Flint's  directions.  The  following  observations  were  made  by 
the  writer  at  Urbana,  Illinois,  on  a clover  field  on  the  University 
Farm. 

6.  Nature  and  Extent  of  In.lury 


Early  in  May,  1921,  the  writer  found  the  young  larvae  of  this 


« . *'i 


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18 

species  in  the  leaf  axils  of  the  clover  plants,  feeding  on  the  young 
leaf  buds  and  riddling  them  with  numerous  holes,  which  increased  in 
size  as  the  leaves  grey/.  Usually  only  one  larva  was  found  in  one 
leaf  bud,  but  rarely  two.  In  no  Instance  has  the  writer  found  three 

In  flower  heads  the  larvae  feed  near  the  bases  of  the  florets. 
Only  one  larva  is  usually  present  in  one  head,  though  occasionally 
two  may  be  found.  A larva  eats  only  a few  of  the  florets  and  pre- 
vents these  from  forming  seeds.  The  greatest  damage  done  by  the 
larvae,  however,  is  in  the  newly  developing  heads,  as  the  larvae 
feed  oh  these  as  they  appear  and  the  damage  results  in  the  mal- 
formation of  the  flowers.  Just  how  much  damage  is  done  by  the  in- 
sect in  this  manner,  the  writer  has  not  been  able  to  determine,  but 
Mr.  Flint  states  that  fifty  per  cent,  of  the  heads  may  be  made  ab- 
normal by  the  larvae  in  this  way  when  the  latter  are  present  in  large 
numbers. 

The  beetles  feed  on  the  leaves  and  malce  numerous  holes,  par- 
ticularly near  the  midribs,  seeming  to  shov/  preference  for  the  young 
growing  leaves.  The  adults  have  been  observed  by  the  writer  resting 
on  clover  heads  in  full  bloom,  but  he  has  not  happened  to  observe 
them  feeding  on  the  florets. 

On  May  17,  1921,  heads  were  picked  at  random  in  order  to  deter- 
mine the  amount  of  Infestation  by  the  larvae.  Out  of  thirty- seven 
heads,  ^rteen  were  found  to  contain  larvae,  i.e.,  thirty-five  per 
cent,  of  the  heads  were  infested.  Of  sixty-four  heads  picked  at  raji- 
dom  from  volunteer  plants  growing  near  First  Street,  Champaign,  tv/en- 
six,  ior  forty;;*  per  cent. , of  the  heads  were  found  to  be  infested. 

Out  of  these  tv/enty-six  heads  infested,  tv/o  heads  contained  two  lar- 
vae each,  one  three  larvae,  and  all  the  others  one  larva  each. 


•I.  : , • ■ " , 

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.20 

7.  Life  History  and  Habi ts 

In  Urbana,  on  April  12,  1921,  active  adult  beetles  were  found 
together  with  adults  of  the  clover  root-curcullo  (Sj tones  hispi- 
dulus) • 

On  April  28,  sweepings  were  begun  in  order  to  determine  the 
abundance  of  this  insect  at  different  periods  of  the  season,  as 
well  as  that  of  the  clover  seed-chalcid,  clover  seed-midge,  and  the 
clover  seed-caterpillar. 

On  May  7,  young  larvae  of  this  species  were  noticed  by  the 
writer  for  the  first  time,  feeding  on  the  young  leaf  buds  of  red 
clover.  The  presence  of  the  larvae  was  easily  detected  by  means  of 
the  feeding  holes  and  the  excreta  on  the  buds.  Several  larvae  were 
collected  and  taken  to  the  laboratory,  where  they  were  confined  in 
vials  and  supplied  with  fresh  clover  leaves  every  day,  the  vials 
being  plugged  with  cotton  to  allow  circulation  of  air.  The  follow- 
ing table  shows  partly  the  life  history  of  the  insect,  as  studied 
by  me: 

Larvae  Date  of  spin-  Date  of  pupation  Date  of  emer- 
ning  cocoon  gence 

1  May  16 May  18 May  23 

2  May  16 May  17 * May  23 

3  --May  16 May  17 May  23 

4-^ May  14 -May  J? May  23 

5 May  16 May  17 May  23 

The  preceding  data  show  that  the  pupal  stage  is  five  or  six 
days,  and  that  the  larva  pupates  one  to  three  days  after  spinning 
its  cocoon.  The  time  spent  by  the  insect  in  the  cocoon,  according 
to  the  preceding  records,  was,  on  the  average,  eight  days.  Herrick 
and  Detwiller  (1919)  found  that,  in  Ithaca,  New  York,  the  period 
spent  by  the  insect  in  the  cocoon,  from  the  time  of  spinning  to  the 


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emergence  of  the  adult,  was  on  the  average,  fourteen  days,  which  is 
almost  twice  as  long  as  the  record  in  Urhana.  Herrick  and  Detwiller 
made  their  observations  during  the  last  days  of  June  and  during 
July,  1919. 

Of  the  larvae  collected  on  May  7,  two  were  confined  together  in 
one  vial.  Both  of  these  spun  cocoons  on  May  12.  One  pupated  on 
May  13  and  the  other  on  the  following  day.  Both  beetles  emerged  on 
the  same  day.  May  20,  with  a difference  of  a few  hours,  the  one  pu- 
pating first,  of  course,  emerging  first.  The  first  adult,  after 
having  emerged,  ate  all  of  its  cocoon  and  after  having  done  this  It 
ate  also  the  caudal  end  of  the  cocoon  of  the  other  insect,  which 
was  already  a fully  developed  adult  but  still  in  the  cocoon. 

On  May  14,  six  adults  were  collected  and  placed  in  a vial.  These 
were  transferred  to  potted  clover  plants  in  the  laboratory  and  a 
chimney  cage  put  over  them.  Two  of  these  beetles  were  in  copula 
upon  transference.  On  May  16,  in  addition  to  numerous  feeding  holes, 
punctures  were  observed  in  the  leaves,  and  an  examination  of  these 
punctures  showed  the  presence  of  minute  elliptical  eggs,  which  were 
those  of  the  beetles.  The  punctures  in  wlilch  the  eggs  were  laid 
were  made  mostly  through  the  upper  epidermis  of  the  leaves,  and  this 
is  probably  the  normal  mode  of  oviposition  in  the  leaves.  The  eggs 
were  mostly  under  the  lower  epidermis,  and  could  be  detected  and 
located  easily  even  with  the  unaided  eye,  since  they  formed  swellings 
on  the  lower  surface  of  the  leaves.  As  a rule,  only  one  egg  is  laid 
in  each  puncture.  In  some  Instances,  however,  two  eggs  were  observed 
together  in  the  same  puncture.  A case  was  observed  in  which  two  eggs 
attached  end  to  end  were  simply  laid  on  the  surface  of  the  leaf.  A 
case  was  also  noticed  in  which  an  egg  was  only  partly  inserted  in  the 


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21 


punc  ture « 

Ovlposition  probably  tak;es  place  at  night,  the  insect  remaining 
rather  inactive  during  the  day. 

The  following  record  was  made  of  the  life  history  of  the  insect 
in  the  laboratory: 


May  14 6 adults  in  captivity. 

May  16 — Eggs  laid. 

May  17 Eggs  have  turned  dark. 

May  23 Eggs  hatched. 

June  4 Larvae  formed  cocoons. 

June  6 Larvae  pupated. 

June  11 Adults  fully  developed  but  still  in  the 

cocoons. 

June  12-13 --Beetles  emerged. 


As  shown  by  the  above  data,  the  eggs  turn  dark  within  one  day 
after  oviposition  and  hatch  in  seven  days.  The  larval  and  the  pu- 
pal stages  are  fourteen  and  five  days  respectively.  Thus  the  insect 
spends  a large  part  of  its  life  in  the  larval  stage.  The  life  cycle, 
from  the  date  of  oviposition  to  that  of  the  eifrgence  of  the  adult, 

A 

is  twenty-seven  days.  The  life-cycle  of  the  insect  out-of-doors  pro- 
bably differs  from  that  in  the  laboratory,  on  account  of  differences 
in  temperature,  moisture,  and  other  factors. 

As  mentioned  previously,  the  eggs  of  the  insect  in  the  labora- 

. ^ field, 

tory  were  laid  in  punctures  in  the  leaf.  In  the^eggs  are  certainly 


not  normally  deposited  in  the  leaves.  Wilderrauth  (V/ebster,  1909) 

finding 

examined  hundreds  of  leaves  without  a single  egg  on  any,  but  he  had 

A 


no  difficulty  whatever  in  finding  the  eggs  under  the  epidermis  of  the 


basal  leaf  sheaths,  more  often  in  groups  of  three. 


Webster  (1909)  made  the  statement  that  cocoons  were  usually 


spun  among  the  full-blooming  heads,  although  one  cocoon  was  found  on 
a clover  leaf  by  Caudell.  Contrary  to  this  observation,  the  present 
writer  has  found  the  cocoons  to  be  more  abundant  attached  to  the 


T . >•  |j'<''< 


■ i.j\n 


. ■ ^ ‘.\‘  ^ 
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22 


lower  surface  of  the  basal  foliage  and  especially  among  the  dried 
leaves  on  the  surface  of  the  ground,  the  cocoons  being  also  attached 
to  these  dried  leaves. 

The  beetle  is  brown  when  fully  developed,  the  color  being  dis- 
tincly  visible  through  the  coarsely  woven  silky  cocoon.  Records  in 
the  laboratory  show  that  a day  usually  elapses  after  the  adult  is 
fully  developed,  before  the  beetle  eats  its  way  out  of  the  cocoon. 

It  assujnes  its  normal  green  color  at  least  three  or  four  days  after 
emergence.  The  temporary  brown  color  has  a significance  in  con- 
nection with  the  determiination  of  the  abundance  of  the  adults  in  the 
field  at  different  periods  of  the  growing  season  and  of  the  number 
of  generations,  as  will  be  seen  subsequently  in  this  paper. 

8.  Abundance 

Graph  No.  IV  shows  the  variation  in  abundance  of  the  adults  as 
determined  by  sweepings.  The  adults  were  still  scarce  betv/een  April 
28  and  May  24,  the  maximum  number  collected  during  this  period  being 
thirty-nine,  on  May  12.  The  adults  began  to  be  collected  in  numbers 
on  May  27,  the  number  collected  on  that  day  being  ninety-one.  The 
number  collected  dropped  to  forty  on  May  28,  increasing  to  one  hun- 
dred and  forty-one  on  May  31,  and  then  to  one  hundred  and  seventy- 
four  on  June  2.  There  was  a drop  again  to  seventy -six  on  June  4,  but 
this  was  followed  by  a sudden  rise  to  four  hundred  and  thirty- seven, 
the  maximum  number  collected,  on  June  9.  The  decrease  in  the  col- 
lections on  June  I3  was  also  sudden,  the  number  collected  on  that 
day  being  one  hundred  and  ninety.  On  June  16,  as  has  already  been 
stated,  the  strip  which  was  being  swept  was  clipped.  The  portion 
of  the  curve  from  June  22  up  to  August  20  does  not  represent  actual 


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collections,  being  computed  chiefly  from  the  figures  obtained  from 
the  strip  in  plot  744,  the  undipped  plot. 

Thus,  according  to  the  preceding  observations,  the  period  of 
abundance  of  the  beetles  extends  from  the  last  days  of  May  to  about 
the  last  days  of  June,  i.e.,  approximately  one  month.  The  beetles 
were  scarce  during  July  and  August  and  thereafter. 

On  May  27  newly  emerged  adults  were  collected  for  the  first 
time  during  the  season.  Then  there  was  an  increase  in  the  col- 
lections from  that  date  onward.  These  newly  emerged  adults  were  of 
the  new  brood,  while  the  beetles  collected  before  May  27  were  pro- 
bably of  the  last  year's  brood.  Out  of  ninety-two  beetles  caught 
with  the  net  on  May  27,  thirty- three  had  recently  emerged,  as  in- 
dics.ted  by  the  brown  color.  Recently  emerged  adults  continued  to 
appear  until  June  30,  after  which  no  more  were  caught  with  the  net. 
Out  of  the  maximum  number  of  adults  collected  on  June  9,  384  had 
evidently  recently  emerged,  and  probably  almost  all  of  those  col- 
lected on  that  day  were  of  the  new  brood. 

The  following  table  shows  the  number  of  newly  emerged  adults 
collected  during  the  period  of  greatest  abundance: 


Date 

No.  collected 

Nev^ly  emerged 

May 

27 

92 

- —29 

n 

28 

-40 

-27 

tf 

31 

141 

- 133 

June 

2- 

174 

144 

ft 

4 

--76--- 

64 

tf 

9 

437 

384 

ft 

13 

--190- 

123 

The  beetle  is,  as  a rule^ nocturnal  in  its  habits,  resting  on 
the  ground  under  rubbish  and  in  between  the  bases  of  the  stems  of 
the  plants  during  the  day,  and  mating  and  doing  most  of  its  feeding 
at  night.  Some  adults,  however,  remain  on  the  plants  during  the  da^^ 


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24 

and  a large  number  do  so  when  the  ground  is  very  moist.  This,  in 
a way,  affects  the  number  of  specimens  collected  with  the -he t.  On 
a day  following  a rain  an  unusually  large  number  of  adults  can  be 
collected  with  a net. 

After  the  clipping  of  most  of  the  plots  on  June  16,  the  beetles 
were  abundant  in  the  stubble  and  under  the  cut  hay,  together  with 
Si tones  flavescens  and  Hyp era  punctata.  On  June  22,  the  new  leaves 
were  observed  to  be  greatly  damaged  by  these  these  three  species, 
being  riddled  with  numerous  holes.  There  is  no  doubt  that  the  com- 
bined injury  by  these  three  species  may  do  much  to  reduce  the  hay 
crop  and  also  to  retard  the  growth  of  the  clover  plants. 

It  seems  reasonable  to  infer  from  the  first  appearance  of  the 
larvae  in  the  field,  the  records  of  the  abundance  of  the  larvae,  and 
from  life  history  records  in  the  laboratory,  that  the  beetles  begin 
to  lay  their  eggs  in  the  latter  part  of  April  and  continue  to  ovi- 
posit through  May.  The  larvae  were  most  abundant  and  did  most  da- 
mage after  the  middle  of  May  up  to  the  middle  of  June,  and  were 
scarce  toward  the  last  days  of  June.  The  period  of  emergence  of 
adults  in  the  field,  as  far  as  my  observations  showed,  ranged  from 
May  27  to  June  30. 

On  June  27,  ten  adults  were  confined  in  the  laboratory  on  potted 
plants,  but  these  did  not  lay  eggs.  Throughout  July  and  August,  no 
larvae  were  observed  in  the  field,  showing  that  the  insect  had  ceased 
to  breed  during  these  months,  although  records  by  Mr.  Spooner  show 
that  the  larvae  have  been  collected  as  late  as  July  17  and  21.  There 
is  probably  only  one  generation  during  May  and  June,  but  oviposit! on 
is  prolonged  over  a considerable  period.  From  May  7 up  to  June  15, 
the  larvae  were  found  in  all  stages  of  development. 


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On  September  20,  a newly  emerged  adult  and  a cocoon  were  col- 
lected by  the  v/riter.  Again,  on  October  6,  a newly  emerged  beetle 
was  found.  All  of  these  records  are  evidences  of  second  generation 
of  beetles,  although  the  insects  of  the  second  brood  are  not  a- 
bundant. 

The  insect  hibernates  as  an  adult  on  the  ground  under  the  dead 
plants  and  other  rubbish  in  the  field  and  in  between  the  stems  of 
the  living  plants. 

9,  Natural  Enemies 

Two  insects  are  known  to  be  parasitic  on  the  larvae  of  Phyto- 
npmus  nlgrirostris.  namely,  a small  fly,  Anisia  species,  near  varia- 
bilis  Coq.,  and  a hymenopteron,  Bracon  sp.,  both  of  which  were  re- 
ported by  Webster  in  1909. 

The  larva  of  this  insect  is  attacked  by  a fungus,  Entomophthora 
sphaerosperma  Pres.,  which  is  also  the  worst  enemy  of  the  larva  of 
Hyp era  punctata.  As  to  the  manner  of  the  attack  of  this  fungus,  on 
tha  larva  of  Hyp  era  punctata.  Titus  says:  "The  fungus  develop;^.^  in 
the  body  of  the  host,  as  a network  of  branching  mycelia,  some  of  the 
branches  push  through  the  ventral  wall  and  become  attached  as  rhi- 
zoids  to  some  surface;  over  the  body  is  formed  a gray  velvety  coa- 
ting of  fine  threads  which  have  penetrated  the  skin;  on  the  tips  of 
some  of  these  are  formed  conldia;  from  these  come  temporary  spores 
which  are  shot  away  from  some  distance  and  may  thus  alight  upon  an- 
other host  and  begin  to  grow.  Resting  spores  develop  inside  the 
host  and  probably  may  thus  live  over  until  the  next  season. 

The  sick  larvae  crawl  up  the  plants  during  the  night,  ascending 
as  high  as  possible;  if  on  a slender  stem  or  a grass  blade  they  coll 


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26 


themselves  about  it  in  a horizontal  position. 

"Arthur  (I885)  states  that  they  die  by  noon,  remaining  in  this 
position,  and  during  the  late  afternoon  have  changed  to  a velvety 
gray.  By  the  next  morning  the  larva  is  only  a blackened  shriveled 
mass. " 

According  to  Dr.  Folsom,  who  published  a detailed  account  in 
1909  of  the  attack  of  the  fungus  on  the  larva  of  Hyp era  punctata 
as  observed  by  him  in  Illinois,  the  fungus  needs  damp  and  not  too 
cold  weather  for  its  development,  and  affects  the  larvae  in  April 
and  May  and  again  in  October  and  November,  but  not  during  the  win- 
ter. Under  these  favorable  conditions,  the  disease  may  kill  the 
larvae  of  Hyp era  punctata  by  the  wholesale. 

The  manner  of  the  attack  of  the  fungus  on  the  latva  of  Phyto- 
nomus  nip;rirostris  is  probably  similar  to  that  on  the  larva  of  Hy~ 
pera.  and  the  extent  of  its  infestation,  under  favorable  conditions, 
may  be  equally  great. 

On  June  2,  1921,  four  cocoons  of  Phytonomus  nl^rlrostris  were 
collected  in  the  field  by  the  writer  and  placed  in  a vial  plugged 
with  cotton.  On  June  16,  1921,  a hymenopterous  parasite  had  emerged 
from  one  of  these  cocoons.  This  was  identified  by  Dr.  C.  P.  Alexan- 
der, entomologist  of  the  Illinois  Natural  History  Survey,  as  Spilo- 
chalcis  torvina  Cress,  and  this  determination  was  later  confiraed 
by  Mr.  Henry  L.  Vierick. 

So  far  as  I have  ascertained  from  available  literature,  this  is 
the  first  record  of  the  species  as  being  parasitic  on  Phytonomus 
nlgrirostris . Titus  (I905)  reported  having  reared  the  chalcid  from 
the  sugar  beet  crown  borer,  Hulstea  undulatella  Clemens,  and  also 
from  the  pupa  of  an  unidentified  tortricid  from  Chino,  California. 


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27 


Cresson  described  the  chalcid  and  gave  Massachusetts,  Connecticut, 
Illinois,  and  Texas  as  its  habitat.  Thus,  according  to  the  pre- 
ceding records,  the  parasite  is  widely  distributed  in  the  United 
States.  Cresson' s technical  description  of  the  species  follows: 

Female — Black,  opaque;  spot  between  antennae,  transverse 
beneath  each  posterior  ocellus,  spot  on  anterior  orbits;  narrow 
posterior  orbits,  and  the  large  mandibles  except  tips,  pale  ye- 
llow; thorax  densely  rugulose;  pro thorax  with  four  whitish  dots 
on  anterior  margin— two  on  each  side  and  two  approximately  above 
—and  a reddish  spot  near  each  posterior  angle;  mesothorax  with 
a short  line  on  each  side  of  middle  lobe  and  two  spots  on  pos- 
terior part  of  each  lateral  lobe,  pale  orange  yellow;  scutellum 
with  a rounded  pale  yellowish  spot  on  each  side,  tegulae  pale 
yellow,  fuscous  posteriorly;  wings  hyaline;  legs  black,  sericeous 
tips  of  anterior  femora,  their  tibia  at  tips  and  within  and  all 
the  tarsi,  except  tips,  yellowish  white;  posterior  coxae  entire- 
ly black;  their  femora  black,  inner  side  with  a yellowish  apical 
spot,  outer  side  with  a spot  at  base  beneath,  a spot  at  tip 
above  and  a transverse  tortuous  band  near  apex,  pale  yellowish, 
sometimes  irregularly  margined  with  brown,  and  interrupted  into 
spots,  femoral  teeth  minute;  posterior  tibiae  black,  with  a 
yellowish  annulus  at  tip  and  another  nbai?  .base;  abdomen  subsifom 
smooth  and  polished,  first  segment  with  a whitish  spot  on  each 
side  between  middle  and  apex,  sometimes  wanting  and  the  second 
segment  with  a large  spot  of  same  color  on  each  side  at  base, 
sometimes  the  fifth  segment  has  lateral  pale  spot;  petiole  ro- 
bust, scarcely  half  the  length  of  posterior  coxae.  Length  . 15- 
.20  inch.  Hab. — ^Massachusetts,  Connecticut,  Illinois,  Texas. 

The  markings  on  posterior  femora  vary  considerably. 

This  hymenopterous  parasite  was  collected  by  the  writer  at  va- 
rious times  in  the  field.  The  following  data  show  the  number  col- 
lected: 


Date  No.  collected 

June  22 2 

June  23 2 

August  4 1 

" 12 1 

»'  24 1 


It  will  be  worth  while  to  ascertain  the  percentage  of  parasitism 
in  future  studies  in  this  locality. 

On  June  16,  1921,  a dead  larva  was  found,  on  examination  of 
which  a hymenopterous  larva  was  found  attached  transversely  to  the 


* -• 


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28 


ventral  aspect  of  the  third  segment,  hut  unfortunately  this 
parasite  succumbed  to  dryness  in  the  laboratory. 

The  carabid  beetles  of  the  species  Calosoma  calidum , were  obt- 
served  in  the  field.  On  July  7,  one  beetle  was  taken  alive  to  the 
laboratory  and  placed  in  a glass  jar,  and  with  it  were  placed  the 
following  insects: 

Four  adults  of  Phytonomus  nigrl rostris 
Two  adults  of  Si  tones  hispidulus 
Three  caterpillars,  species  unknown. 

On  July  8,  all  of  these  insects  were  found  to  have  been  devoured 
by  the  beetle,  leaving  only  such  apparently  unedible  portions  of  the 
bodies  of  the  adults  of  Phytonomus  and  Si tones,  as  the  elytra  and 
portions  of  the  legs.  It  seems  probable,  then,  that  this  carabid 
preys  on  Phytonomus  nig;rirostris  in  the  field  also. 


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29 


VIIi:  POLLINATION  OF  RED  CLOVER 


II.  INSECTS  OBSERVED  WORKING  ON  CLOVER  HEADS 


Red  clover  ie  a plant  which  is  entirely  dependent  upon  insects 
for  it  fertilization.  Of  the  insects  that  pollinate  red  clover,  the 
humble^ees  are  the  most  important.  It  is  estimated  that  the  United 
States  is  indebted  to  bumblebees  to  the  amount  of  |60. 000,000  an- 
nually for  their  work  as  pollinators  of  red  clover,  to  say  nothing 
of  other  farm  crops. 

The  abundance  of  bumblebees  in  a particular  locality  varies 
from  year  to  year.  During  the  past  season,  for  example,  bumblebees 
were  not  observed  in  numbers  in  clover  fields  at  Urbana,  and  this 
certainly  accoiints  to  a large  extent  for  the  extremely  low  yields 
of  red  clover  here  reported. 

The  importance  of  bumblebees  as  pollenizers  depends  upon  their 
numbers  when  the  clover  field  is  in  full  bloom.  In  Illinois,  bumble- 
bees are  considered  most  important  pollenizers  of  the  second  crop 
of  clover,  for  the  workers  are  abundant  in  late  July,  August,  and 
September.  They  are  not  important  as  pollenizers  of  the  first  crop, 
for  in  Jime  the  only  bumblebees  on  the  wing  are  a few  queens  that 
have  survived  the  winter  and  these  do  not  do  much  pollinating  as 
they  stay  most  of  the  time  in  the  nest.  It  is  a well  known  fact, 
therefore,  that  the  first  crop  of  clover  is  not  pollinated  by  bxmible- 
bees  to  any  appreciable  extent. 

In  a recent  paper.  Dr.  Folsom  made  the  statement  that  twenty 
years  ago  in  Illinois,  it  was  taken  for  granted  that  there  was  not 
enough  seed  in  the  June  crop  to  pay  for  its  extraction.  Since  then, 
however,  farmers  in  the  state  in  increasing  number  have  found  it 


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profitable,  ;now  and  then,  to  cut  the  June  crop  for  seed  instead  of 
hay,  and  have  obtained  i Lniiiuiikljln  yields  of  from  one  half  a bushel 
to  two  bushels  of  seed,  and  possibly  more,  per  acre. 

This  being  the  case,  the  question  as  to  how  the  June  crop  is 
pollenized  needs  to  be  ansv/ered.  Dr.  Folsom  has  learned  from  va- 
rious sources  that  in  a few  instances  the  yield  of  seed  had  occurred 
in  a region  where  Italian  honey  bees  were  common  and  had  been  ob- 
served working  on  the  flowers.  Dr.  A.  D.  Hopkins  and  Dr.  Folsom 
have  both  found  out  that  honey  bees  of  this  race  are  no  doubt  im- 
portant  pollenizers.  There  ^ however,  cases  reported  in  which  yields 
of  clover  seed  had  been  obtained  in  places  where  the  honey  bees  did 
not  occur,  so  that  in  the  words  of  Dr.  Folsom,  "there  still  remained 
some  mystery  as  to  how  the  June  crop  is  pollenized." 

Now,  according  to  Dr.  Folsom,  Mr.  W.  P.  Flint  has  dn  several 
occasions  observed  a species  of  bee  belonging  to  the  genus  Tetralonle 
sucking  the  florets  of  red  clover  in  June,  and  has  several  times  re- 
ceived the  same  bee  from  observant  farmers,  who  noticed  its  abundance 
in  the  clover  fields. 

After  the  middle  of  May,  1921,  the  writer  observed  a species  of 
bee  working  on  the  heads  of  clover.  This  bee  was  later  identified 
by  Vierlck  as  Tetralonia  dilecta  Cress.  Its  presence  in  large  num-  I 
bers  in  the  field  attracted  attention  to  such  an  extent  that  Dr.  Fol- 

t-he  wy  ’i'ter 

som  and  undertook  to  make  some  observations  and  perform  experiments 
in  order  to  find  out  whether  this  species  of  Tetralonia  and  other 
species  observed  in  the  field  pollenize  red  clover  or  not.  On  May 
24,  Dr.  Folsom  took  a root  cage  with  parallel  glass  sides  to  the  clo- 
ver field;  in  it  was  placed  a solid  row  of  clover  heads  in  full  bloom 
and  then  several  individuals  of  Tetralonia  dilecta  were  introduced 


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31 


into  the  cage.  Some  of  the  bees  worked  on  the  blossoms,  their  ope- 
rations being  studied  under  a hand  lens.  Examination  under  the  mi- 
croscope of  the  mouth  parts  of  specimens  collected  from  the  field 
that  had  previously  been  observed  working  on  the  heads  of  clover 
showed  the  presence  of  many  pollen  grains,  especially  on  the  mentum, 
but  also  on  the  maxillae.  As  a matter  of  fact,  pollen  grains  were 
observed  sticking  almost  everywhere  on  the  ventral  aspect  of  the 
mouth  parts,  these  pollen  grains  being  indistinguishable  from  those 
of  red  clover. 

Tetralonia  dilecta  Cress,  belongs  to  the  family  Euceridae,  a 
family  of  solitary  digger  bees  with  but  one  male  and  one  female  to 
each  nest.  The  two  sexes  of  the  species  are  so  different  from  each 
other  in  general  appeaij^ce,  the  female  resembling  the  honey  bee^  that 
it  may  be  mistaken  for  the  latter,  so  that  one  who  is  not  familiar 
with  the  sexual  individuals  will  take  them  to  be  distinct  species. 
For  Instance,  we  erred  at  first  in  calling  the  male  Mellssodes  obli- 
qua  Say.  For  these  reasons,  it  seems  desirable  to  give  in  this  pa- 
per brief  descriptions  of  the  sexes  in  order  to  enable  the  collector 
or  observer  to  recognize  them  in  the  field. 

Male.  The  clypeus  is  yellow  euid  is  sparsely  pubescent.  The  pu- 
bescence of  the  thorax  and  of  the  legs  is  usually  of  a much  lighter 
color  than  that  of  the  female,  being  light  yellow  or  nearly  grayish. 
The  antennae  are  longer  than  those  of  the  female,  reaching  to  the 
base  of  the  abdomen.  The  male  measures  about  1.2  cm.  in  length. 

F^ale.  The  clypeus  is  black  and  more  hairy  than  that  of  the 
male.  The  pubescence  of  the  thorax  and  of  the  legs  is  brownish  ye- 
llow. The  whit^'  l^ransverse  bands  of  hairs  on  the  abdomen  are  mor^ 


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32 


pronounced  than  those  of  the  male.  The  antennae  extend  to  about 
the  middle  of  the  thorax  a little  caudad  of  the  base  of  the  anterior 
v/ing.  The  female  measures  from  1.5  to  1.7  cm.  in  length. 

Specimens  Of  Tetralonia  dilecta  were  first  observed  and  col- 
ted  by  the  writer  on  May  17,  1921,  when  the  first  heads  of  clover 
were  just  beginning  to  bloom.  On  May  24,  the  bees  were  abundant 
and  a few  days  after  this  Dr.  Folsom  and  I began  our  experiments. 

On  June  30,  the  bees  had  disappeared,  showing  that  the  period  of 
activity  of  the  species  was  approximately  forty-four  days. 

A second  bee  of  importance,  Melissodes  blmaculata  Le  P.,  ap- 
peared on  July  5.  This  bee  has  also  been  observed  working  on  the 

florets  of  clover  and  examination  of  the  mouth  parts  showed  the  pre- 

is 

sence  of  pollen  grains  of  red  clover.  This^a  black  bee,  belonging 
to  the  same  family  as  Tetralonia  dilecta  Cress.  As  in  Tetralonia. 
the  male  has  longer  antennae  than  the  female,  as  is  characteristic 
of  the  family  to  which  these  insects  belong. 

Male.  The  male  is  slightly  smaller  than  the  female,  measuring 
about  1.1  cm.  The  clypeus  is  yellow.  The  pubescence  of  the  middle 
and  posterior  tibiae  and  the  metatarsus  of  each  posterior  leg  is 
white.  The  male  lacks  the  two  spots  on  the  abdomen,  which  are  pre- 
sent in  the  female. 

Female.  The  female  measures  from  1.2  to  1.3  cm.  in  length.  The 
clypeus  is  black.  The  posterior  legs  are  more  distinctly  pubescent 
than  the  corresponding  legs  of  the  male,  and  their  pubescence  is 
brownish  yellow  instead  of  white,  as  in  the  male.  The  fourth  dorsal 
abdominal  segment  has  an  apical  patch  of  white  hairs  on  each  side; 
hence  the  name  of  the  species. 

IrPdividuals  of  this  species  were  first  observed  in  the  field  on 


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33 

July  5,  but  were  not  abundant  then.  On  July  9,  the  bees  were  pre- 
sent in  large  numbers  and  remained  so  until  August  5,  after  which 
they  became  scarce,  disappearing  on  August  13.  The  period  of  acti- 
vity of  this  species,  therefore, was  approximately  forty  days. 

Besides  these  two  species  that  have  been  described,  there  are 
other  bees  of  less  importance  that  were  observed  working  on  the 
heads  of  clover.  Among  these  are  two  species  of  MeRachile.  latima- 
nus  Say  and  brevis  Say,  both  of  which  belong  to  the  family  Megachl- 
lidae,  a family  of  leaf-cutters.  The  members  of  this  family  have 
the  habit  of  making  cells  for  their  young  out  of  neat^-y-cut  pieces 
of  leaves.  Of  the  two  species  mentioned,  brevis  was  observed  to  be 
present  in  larger  numbers  and  seems  to  be  the  better  pollinator  of 
the  two.  Megachile  latimanus  is  the  more  alert,  and  is  most  of  the 
time  on  the  wing,  and  is  easily  disturbed  by  the  approach  of  the 
collector.  This  species  has  the  habit  of  darting  swiftly  past  the 
collector,  and  it  was  while  the  insects  were  in  the  act  of  darting 
that  the  writer  caught  all  of  his  specimens. 

Small  bees  of  the  genus  Halictus  were  also  observed  by  the  writer 
working  on  the  heads  of  red  clover. 

A species  of  fly  , Exoprosona  prorsa.  was  likewise  observed  sucl^- 
ing  the  florets  of  clover.  This  fly  was  first  collected  by  the 
writer  during  the  past  season  on  July  19.  It  was  present  in  consi- 
derable numbers  August  16,  after  which  it  became  scarce,  disappearing 
on  August  25.  Thus  its  period  of  activity  was  approximately  forty 
days. 

Examination  of  the  mouth  parts  of  this  fly  failed,  however,  to 
show  the  presence  of  pollen  grains.  This  is  due  to  the  fact  that  the 
mouth  parts  are  smooth  and  destitute  of  setae  to  which  the  pollen  | 


'•  ' sv. 


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34 


grains  may  attach  themselves.  The  absence  of  pollen  grains,  howevei; 
on  the  mouth  parts  is  not  sufficient  evidence  that  the  fly  does  not 
pollinate  clover  to  some  extent. 

In  addition  to  the  insects  that  have  already  been  mentioned, 
thrlps  were  found  in  great  abundance  in  clover  heads  and  these  in- 
sects are  thought  to  pollinate  red  clover  accidentally. 

2-.  COMPARISON  OP  THE  ACTIVITY  OP  THE  BEES 


With  the  object  of  comparing  the  activity  of  the  different  bees 
observed  in  the  field,  data  were  obtained  as  regards  the  number  of 
heads  visited  and  of  the  number  of  florets  sucked  by  them  per  mi- 
nute. In  order  to  have  a sound  basis  of  comparison,  the  observation} 
were  made  at  periods  when  most  of  the  heads  were  in  full  bloom.  The 
following  tables  show  the  data  obtained. 

Name  of  insect  No.  of  heads  Total  No.  Average  No.  of 

visited  per  of  florets  florets  sucked 
minute  sucked  per  per  head, 

minute 

Bombus  pennsylvanicus 6 39 6.5 

6 -26 4.3 


4- 

4- 
6 
3 
6 
5 

3 
5 

4 

5- 

5- 

6- 


•46. 

•32- 


•A  1.5 
• 8.0 


•38. 

•28- 

:28. 


•8.0 

•6.0 


Average- 


■35* 


Bombus  separatus- 8- 

5* 

8- 


Average 


o. 


-42- 

‘31* 

•38. 

•22- 

•33- 


-7.0 

•5.2 

•6.2 

*4.7 

■2,4 

•4.5 


' 


• 1 , -*  • I 


. 'Vr.t'd.',,  t\ 

' ''  ■'  ' \ 

u* • .-i  Vi.  '-(My. 


^ .i.* 


'tt!^,i'£-'  '■•. ’J.‘ 


1 'j  '■>€>  '■  '■■  ;■  -.f  f <j 


35 


Name  of  insect 


Tetralonia  dilecta- 
(Female) 


Average 

Tetralonia  dilecta 

(Male) 


Avera.ge 

Melissodes  bimaculata' 


Average 

Megachile  brevis 


Average 
Apis  mfclltfera 


Average 


No.  of  heads 

Total  No. 

Average  No.  of 

visited  per 

of  florets 

florets  sucked 

minute. 

sucked  per 
minute 

per  head 

8 

10 

-1.2 

9 

13 

1.4 

9— 

12- 

1.3 

8 

12 

-1.3 

6 

5 

4 

3 

1 

1 

36 

- 18 

— -12 

- -10 

- 12 

8 13 

zJi. 


•4 17 2.7 

■4 16- -4.0 

3 13 4.3 

3  11 3.7 

5 — 16 3.2 

4  15 3.7 

2  15 —7.5 

3  15 5.0 

7 19 2.7 

8--- — 19~‘~ --2.3 

4  -15 4.0 

2-- -12- 6.0 

5  9 1.8 

3 9 3.0 

4-— 11- 2.7 

3 9 3.0 

2 - 9--- --4.5 


•3 10 3.0 

5 17 3.4 

3 - — 12---- 4.0 

8 17 2.  1 

3 12 —4.0 

5  15 2.6 

3 -12-- 4.0 

6  --14 --2.3 


14- 3.0 


1 .6 

Jill 


r It  - '•  ' ' . • ' T - 47  ' V T vv¥ ’ -s  f. 

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?.  


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,'•■  . _ ■ :ta  ^ "1'  ^ 


^ ♦ -»  ~ *"  * * y . ■ « ' ’ "'  I ^ ^ ‘ * * 4 T’'  \ 

FJjt' ■ Ci  ,/■“■“■"•*■"••“■*«  ■■••*»♦  Jr,  I “■«••♦  V4fMi»i.l»  - I"  . j’iW'.iV  ' ’ ' ■'  '.  ' * ' ,4  "'  * ' • * ' 

"/j"  f « ' t »*’*  ■».*»^  » -« y '\'V(|  -«  -K  •«.■»  i«  -'  f.  ,»  L M m jBS'' 

•**"*'  " " “ *■'■’ 

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,t- \''-^  ."T- A - -MW-*  • <*v«»  «tw  •"  W .•,'*•  ’ , jji 

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. , •_  V ,,  - (.  . '^.  , .■  44^.  . 


^ S.  w <«-w  «»  *4^  W[«r' y » *••*•••» /’A *'  ^ 

■till  II  ||^|jyi>4yy^s.-  * ' '' 


36 


The  preceding  data  may  he  siimmarized  in  the  following  table: 


Name  of  insect  Average  Average  No.  Average  No. 

No.. of  heads  of  florets  of  florets 

visited  per  sucked  per  sucked  per 

minute  minute  head 

Borabus  pennsylvanicus 5 35 7 

Bombus  separatus 7 33 4 

Tetralonia  dilecta  (Female) — 8--- 12 1 

Tetralonia  dilecta  (Male) 4 17 3 

Melissodes  bimaculata 4 15 — 4 

Megachile  brevis 3 10 3 

Apis  mfcllifera 5 14 3 


(Note:  In  figuring  out  the  averages,  decimals  exceeding  0.5 
were  taken  as  unity.) 

Although  the  preceding  observations  are  somewhat  meager,  yet 
they  are  presented,  for  they  give  some  idea  as  to  the  relative  ac^. 
tivity  of  the  bees  in  pollination.  The  last  table  summarizing  the 
data  obtained  speaks  for  itself.  It  appears  that  the  bumblebees, 
Bombus  p ennsy 1 vani cu s and  Bombus  separatus.  sucked  more  florets 
than  the  other  bees  here  listed.  B.  pennsylvanicus  visited  from 

three  to  six  heads  per  minute,  the  average  being  five,  and  sucked 
florets  in  each  head  ranging  from  twenty- six  to  forty- six,  the  ave-  j 
rage  being  thirty- five.  The  average  number  of  florets  sucked  by 
this  species  per  clover  head  is  seven.  B.  separatus  visited  more 
heads  per  minute  than  B.  pennsy Ivani cus . but  sucked  fewer  florets 
per  minute^ per  head.  Of  the  sexes  of  Tetralonia  dilecta.  the  femaleJ 
as  the  figures  show,  visited  more  heads  per  minute  than  the  male  but 
sucked  fewer  florets  in  the  same  period  of  time.  The  male,  there- 
fore,* o;f  this  species  may  be  regarded  as  the  better  pollinator. 

There  is  not  much  appreciable  difference,  however,  between  the  male 
Tetralonia  dilecta  and  Melissodes  bimaculata  and  the  Italian  honey 
bee.  Apis  mglll f era,  in  this  respect.  Megachile  brevis  stands  some- 


f 


> > 

, lij'v 


..  \ 'J  ‘ » 


<■  ; 


i' 


f 


; i'  < '..'st4\^i 

«•  ^ 

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•••:'.-V)  -.trrCiXJS 

.... 

•*-••• --v 

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.,  » off 

* - - -«*-r  - 

• ' -i,« .•■  i.  . tj.*’.::  l<j  ^ ■ 

.r»,^i  ‘k 

-—--if. 

. » *,  .i  •«  „ 'S*’"  «»*■'  * 

r»»  #\  ‘ 

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, • ( I'fti  :•' 

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- . » 

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T;v:  ;>  -.Vu^ 

» 

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— r ■ '•■•  ■ *^  . '■.;v;^„^ 

I ia^yC*i» iftnr"  -t:— 


r*  -T 


37 

what  below  these  three  last  bees  mentioned  in  the  number  of  heads 
visited  and  in  the  number  of  florets  sucked  per  minute. 

.3 . EXPERIMENTS  ON  POLLINATION  OF  RED  CLOVER 

The  statement  has  already  been  made  that  Tetralonia  and  Melis- 
sodes  were  observed  thrusting  the  proboscis  into  the  florets  of  red 
clover  blossoms  and  that  examination  of  their  mouth  parts  showed 
the  presence  of  numerous  pollen  grains,  especially  on  the  tongue 
and  maxillae,  which  were  indistinguishable  from  those  of  red  clover. 
These  observations,  however,  are  not  alone  sufficient  to  justify 
the  conclusion  that  these  bees  pollinate  red  clover.  It  was  neces- 
sary to  perform  experiments  to  determine  whether  clover  heads  on 
which  the  bees  had  worked,  and  from  which  other  insects  had  been  ex- 
cluded, would  produce  seeds.  Clover  plants  with  unopened  buds  were 
carefully  dug  up  from  the  field  and  transplanted  to  flower  pots  of 
about  twenty  centimeters  in  diameter.  All  heads  which  were  in  full 
bloom  were  of  course  removed  from  the  plants.  These  potted  plants 
were  placed  out-of-doors  on  bigger  pots  of  about  thirty- four  centi- 
meters in  diameter  filled  almost  to  the  top  with  soil.  The  plants  I 
were  then  protected  with  cylindrical  wire  cages  of  about  forty-eight 
centimeters  in  height  and  forty-five  centimeters  in  diameter  and 
with  a mesh  of  one  millimeter.  When  some  of  the  heads  began  to  bloom 
bees  were  collected  from  the  field  and  turned  loose  in  the  cage. 

. Experiment  with  Tetralonia  dilecta  Cress. 

Clover  plants  with  unopened  buds  were  potted  on  May  25.  On  May 
26,  some  of  the  clover  heads  were  in  bloom  and  Dr.  Folsom  put  thirty 
individuals  of  T.  dilecta  into  the  cage.  Some  of  the  bees  were  ob- 


4^ 


• ^ ^ “‘*  • - ■ ; ' ^ * ..  i. . JL;r  ^..,  . .. 


^iRVf  4^R«;r 

/■'  B , .:  -js,y/::p  ..^^  -:^  ' ' ' ' - “**  ■ 


lliW^''"'*  -■■•- 


:l*il£jk5jL-I  apa'e  4fii>ti?o^4i?3''f'4lTv.!l 

U*.’  ■ . ' ’*<  . ‘»V  .^‘  ■ ■ .'  . • >'■  • ' ■ f'  ‘ ‘v 


,• 


JS 


m 


.r'r  M,  r$4" ‘^'»VcXo  t>#J^iH'.v<  mJ  ' <»yvo't't«g^’.|^OT 

ajtiirtoty  xHific  r.cyt*. 


twr  i'en^ijcC'A'  feJlTjiiXt ''£.^il'»^t:i,i.'' 


44;^  . 

'*tro'5-x^W^i(v'  Ativ^  Vc-.^iie  'TBSI'M 

■ *•  ■ . -*■*  ^..  f'’’*'i^‘ • •'..  ’ -V  >>’'*  *x  r. 


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, . '■^-•‘i'texw  JEIC.1  •vrilt 

if^'.  ■ ^ -'A'v-  ■ ■■'.n‘‘.'  ' •’  ’■  '■  * V,;».|i-  * 

i‘  )■-'  ' ■ ■ ' ■ i ^.  , < ■'  ’ ..  ' tf  rSlpW 


BCi?:cr'  r.j.  ifc^vtr-.  .♦dJ  U" 


s : *' 


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■*■  . '.  ■ rf  ’ ' ^ ' '4  » ^ •‘■ill*'  a\-\.Jtt.mk 

:■ ■'  ,*'.  ■ , 

f , ' ■ . si 


f,  r’.'  \-s  ' : ,'® 


!»*-»y«ii-  ■ ->^  *Iyi . .TWyi*.'  • *:*»mv^  v^yi 

W . 


38 


served  working  on  the  flowers  on  the  same  day.  After  twenty-four 
hours,  all  of  the  hees  had  died.  Five  days  later.  May  31,  the 
writer  put  four  males  and  three  females  into  the  cage,  and  some  of 
these  were  also  observed  working  on  the  flowers.  These  bees  also 
died  after  twenty-four  hours.  It  was  observed  that  the  bees,  soon 
after  being  turned  loose  in  the  cage,  rested  and  crawled  on  the 
wire,  especially  near  the  top  of  the  cage,  and  attempted  to  find 
their  way  out.  In  their  flight  within  the  cage,  however,  some  of 
the  bees  struck  the  clover  heads  and  in  this  way  carae  to  find  them 
and  work  on  the  florets.  For  this  reason,  in  order  that  the  bees 
could  find  the  flowers  more  readily,  it  v/as  found  necessary  to  raise 
the  pots  in  such  a way  that  the  clover  heads  would  be  as  close  to 
the  top  as  possible. 

The  writer  did  not  have  any  difficulty  in  catching  the  bees  in 
the  field.  In  the  act  of  sucking  the  florets,  they  did  not  seem  to 
mind  the  slightest  interruptions  and  were  easily  caught  by  the  use 
of  a wide-mouthed  bottle. 

On  July  1,  the  clover  heads  had  dried  and  were  picked  for  seeds. 
From  789  florets,  not  counting  undeveloped  florets  which  could  not 
have  been  pollinated.  Dr,  Folsom  and  the  writer  obtained  1?1  seeds, 
showing  that  tv^entjr-one  per  cent,  of  the  florets  had  been  pollenlzed 
by  Tetralonia. 

, Experiment  v/lth  Melissodes  bimaculata  Le  P. 

Clover  plants  for  this  experiment  were  potted  on  July  12.  Two 
days  later,  when  some  of  the  flowers  were  beginning  to  bloom.  Dr, 
Folsom  put  seven  individuals  in  the  cage  at  2:30  p.m,,  and  he  ob- 
served one  of  these  working  on  the  heads  ten  minutes  later.  On  July 


16,  the  writer -introduced  eleven  bees,  and  on  July  19,  five  more. 
Some  of  these  were  also  observed  working  on  the  heads.  In  all  -a 
total  of  twent3r- three  bees  had  been  Introduced  into  the  cage. 

These  bees  behaved  in  the  cage  in  much  the  same  way  as  did  the 
Tetralonia  individuals,  and  like  the  latter  did  not  live  long  in 
the  cage.  Most  of  them  died  after  twenty-four  hours. 

Melissodes  bimaculata  is  much  more  active  on  the  wing  than  Te- 
tralonia dilecta.  and  the  author  had  some  difficulty  in  collecting 
specimens  for  the  pollination  experiment  by  means  of  a wide-mouthed 
bottle  and  found  it  necessary  to  use  the  insect  net. 

On  August  4,  1921,  the  writer  picked  the  dried  heads  and  exa- 
mined them  for  seeds.  As  several  beeS' had'. been  observed  working  on 
the  heads.  Dr,  Folsom  and  the  writer  expected  to  get  some  seed,  but 
when  the  heads  were  exarained  the  216  florets  counted  gave  only  two 
seeds.  Thus  the  results  of  this  experiment  were  negative, 

A second  experiment,  however,  with  the  same  insect  gave  much 
better  results.  Plants  for  this  experiment  were  potted  on  July  21 
and  were  given  the  same  080*6  as  those  in  previous  experiments.  On 
July  23,  some  of  the  flowers  were  in  full  bloom  and  the  writer  put 
fifteen  individuals  of  bimaculata  into  the  cage.  On  Jul3^  25, 
sixteen  more  bees  were  Introduced;  thus  thirty-one  bees  were  used 
in  this  experiment.  Many  of  these  bees  were  observed  working  on  the 
heads.  On  August  12,  the  heads  were  picked  for  seed.  Seven  heads 
gave  a total  number  of  two  hundred  and  ninety-three  florets^ from 
which  ninety  seeds  were  obtained.  This  experiment  showed  that  Me- 
lissodes  bimaculata  Le  P.  pollinates  red  clover. 


40 


. Experiment  with  Exoprosopa  prorea 

Plants  for  this  experiment  were  potted  on  July  26,  Two  days 
later,  July  28,  when  some  of  the  heads  were  in  bloom,  the  writer  in- 
troduced ten  flies  into  the  cage.  The  flies,  after  a fev/  minutes 
in  confinement,  sta^yed  almost  invariably  on  the  sides  of  the  cage. 
None  of  these  flies  was  observed  v/orking  on  the  heads.  In  the  morn- 
ing of  July  29,  only  two  flies  remained  alive^tUie  were  still 
on  July  50,  showing  that  these  insects  live  a little  longer  in  con- 
finement than  individuals  of  Tetralonia  dilecta  and  Melissodes  bima- 
culata.  On  July  30,  twelve  more  flies  were  introduced  into  the  cage. 
Some  of  these  were  observed  working  on  the  clover  heads. 

On  September  16,  the  heads  were  examined  for  seeds.  It  is  only 
necessary  to  mention  that  the  nine  heads  obtained,  in  this  experiment 
produced  no  seeds. 

Thus  the  results  of  this  experiment  were  negative, 

. Experiment  with  Megachlle  brevis  Say 

As  in  the  preceding  experiment,  the  plants  used  were  potted  on 

July  26.  Only  two  bees  were  used  in  this  experiment  but  the  insects 

the 

worked  very  Industriously  on  the  clover  heads,  Llke^other  bees  ex- 
perimented with,  individuals  of  M,  brevis  do  not  live  long  in  confine 
ment. 

The  results  of  this  experiment  were  not  .conclusive,  as  only  three 
seeds  were  obtained  from  twelve  heads.  It  must  be  remembered,  how- 
ever, that  the  first  experiment  with  Melissodes  bimaculata  gave  si- 
milar results. 


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41 


In  connection  with  the  preceding  experiments,  red  clover 
plants  with  heads  in  bloom  removed  and  ijaving  only  unopened  buds, 
were  planted  in  two  pots.  These  potted  plants  were  used  as  controls 
They  were  placed  out-of-doors  and  covered  with  wire  cages  just  as 
in  the  preceding  experiments,  but  no  bees  were  introduced  into  the 
cages.  When  the  heads  were  picked  and  examined,  one  of  the  pots 
gave  357  florets^ all  of  which  were  without  seeds.  The  other  pot 
gave  287  florets,  which  were  likewise  seedless. 


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REFERENCES 

Cooley,  R.  A.  1916.  Insect  Pests  of  T915»  Thirteenth  Ann.  Rept. 

State  Ent.  Montana,  Bull.  109,  Mont.  Agr.  Exp.  Sta.,  p.  154. 
Cresson,  E.  T.  l American  Hymenopterar- Synopsis  of  the  North 

American  Species  belonging  to  Genera  Leucospis,  Smicra,  and 
Chalcis.  Trans.  Amer.  Ent.  Soc.,  V.  4,  pp.  29-60. 

Folsom,  J.  W.  1909.  Insect  Pests  of  Clover  and  Alfalfa.  Bull. 
134,  111.  Agr.  Exp.  Sta. 

Herrick,  G.  W. , and  Detwiller,  J.  D.  1919.  Notes  on  Some  Little- 
Known  Pests  of  Clover.  Jour.  Econ.  Ent.,  V.  12,  pp.  206-209. 
Houghton,  C.  0.  1908.  Notes  on  the  Lesser  Clover  Leaf-Weevil. 

Jour.  Econ.  Ent.,  V.  1,  p.  297. 

Titus,  E.  G.  1905.  The  Sugar  Beet  Crown-Borer.  Bull.  54,  U.  S. 
Bur.  Ent.,  pp.  34-40. 

Titus,  E.  G.  1911.  Genera  Hypera  and  Phytonomus  in  America, 

North  of  Mexico.  Ann.  Ent.  Soc.  Amer.,  V.  4,  pp.  3B3-474. 
Webster,  F.  M.  I909.  The  Lesser  Clover  Leaf-Weevil.  Bull.  85, 

U.  S.  Bur.  Ent. 


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